Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$43.48	3.579%	$45.0361	$45.04	$45.05	$45.00
Purchase #2	$192.88	3.406%	$199.4495	$199.45	$199.45	$199.40
Purchase #3	$239.61	4.595%	$250.6201	$250.62	$250.60	$250.60
Purchase #4	$234.37	12.771%	$264.3014	$264.30	$264.30	$264.30
Purchase #5	$141.48	6.390%	$150.5206	$150.52	$150.50	$150.50
Purchase #6	$94.27	11.321%	$104.9423	$104.94	$104.95	$104.90
Purchase #7	$177.89	11.182%	$197.7817	$197.78	$197.80	$197.80
7 purchase totals =	$1,123.98		$1,212.6517	$1,212.65	$1,212.65	$1,212.50